Re: [ID 19991229.003] perl 5.005_03 core dumps -- signal

[Joshua N Pritikin <joshua.pritikin@db.com>]

On Wed, Jan 12, 2000 at 10:56:06AM -0500, dan@sidhe.org wrote:
> At 10:35 AM 1/12/00 -0500, Joshua N Pritikin wrote:
> >On Wed, Jan 12, 2000 at 10:18:24AM -0500, dan@sidhe.org wrote:
> > > In some ways its worse. Because threads are really separate processes,
> >
> >What's the difference?  Memory sharing is the same, right?
> 
> Yes, though there's more to a thread than memory sharing. (You can 
> currently flock yourself into a deadlock too, FWIW, though hopefully 
> they're fixing that, too)

Yah, they're definitely aware of that.

> > > only the thread that actually gets the signal delivered can see it.
> >
> >Yes.  That's one of the reasons I felt that linux might be an
> >improvement over the POSIX mess.
> 
> In some ways it is, for the synchronous signals--they're more installed 
> error handlers than anything else. Async signals, on the other hand, are 
> events rather than errors, and are delivered to the *process*, not to the 
> thread. Who should get SIGHUP, or SIGCHLD, or SIGCONT, or SIGIO? These all 
> deal with process-level events, and the thread that was responsible for 
> them being generated (if you can even figure that out easily) isn't 
> necessarily going to be the one that should handle them.

I don't know.  At least the control is in the hands of the developer. On
the other hand, perhaps POSIX provides this as an option too.  I am
hardly qualified to debate this stuff.

> >I never understood the alure of routing all the signals to a single
> >signal-handling thread.  Can anyone comment on this?
> 
> It makes handling the event signals easier. You just route 'em all to a 
> single thread that deals with them, rather than having to cope with them in 
> all your threads.

I'm still mystified.  Obviously the library/kernel can do this
automatically but what is so hard about doing it at the application
level?  Wouldn't it just be a matter of adding a bunch of handlers
to the children threads:

  static Signal_t process_sighandler(int sig) { kill(ParentPID, sig); }

Am I missing something?

-- 
"Never ascribe to malice that which can be explained by stupidity."
                            via, but not speaking for Deutsche Bank

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Follow-Ups from:

Dan Sugalski <dan@sidhe.org>

References to:

Joshua N Pritikin <joshua.pritikin@db.com>
Dan Sugalski <dan@sidhe.org>

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